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More than one way to be a giant: Convergence and disparity in the hip joints of saurischian dinosaurs

Tsai, H P; Middleton, K M; Hutchinson, J R; Holliday, C M


H P Tsai

K M Middleton

J R Hutchinson

C M Holliday


Saurischian dinosaurs evolved seven orders of magnitude in body mass, as well as a wide diversity of hip joint morphology and locomotor postures. The very largest saurischians possess incongruent bony hip joints, suggesting that large volumes of soft tissues mediated hip articulation. To understand the evolutionary trends and functional relationships between body size and hip anatomy of saurischians, we tested the relationships among discrete and continuous morphological characters using phylogenetically corrected regression. Giant theropods and sauropods convergently evolved highly cartilaginous hip joints by reducing supraacetabular ossifications, a condition unlike that in early dinosauromorphs. However, transitions in femoral and acetabular soft tissues indicate that large sauropods and theropods built their hip joints in fundamentally different ways. In sauropods, the femoral head possesses irregularly rugose subchondral surfaces for thick hyaline cartilage. Hip articulation was achieved primarily using the highly cartilaginous femoral head and the supraacetabular labrum on the acetabular ceiling. In contrast, theropods covered their femoral head and neck with thinner hyaline cartilage and maintained extensive articulation between the fibrocartilaginous femoral neck and the antitrochanter. These findings suggest that the hip joints of giant sauropods were built to sustain large compressive loads whereas those of giant theropods experienced compression and shear forces.


Tsai, H. P., Middleton, K. M., Hutchinson, J. R., & Holliday, C. M. (2020). More than one way to be a giant: Convergence and disparity in the hip joints of saurischian dinosaurs. Evolution,

Journal Article Type Article
Acceptance Date Apr 21, 2020
Publication Date May 20, 2020
Deposit Date May 21, 2020
Publicly Available Date May 21, 2021
Journal Evolution
Print ISSN 0014-3820
Publisher Wiley
Peer Reviewed Peer Reviewed
Public URL


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